Fishing tools are known to snag and to retrieve cables from wells. The classical technique of such an arrangement is to provide a body with some upwardly-directed hook-like members to move below a cable, and then upward to snag the cable and bring it to the surface. There is a substantial problem involved in the use of this type of fishing tool, which is that if the tool itself goes beyond the bottom end of the oil well pipe or tube, and then the fishing tool is pulled up, the tool can snag on the bottom of the tube and can destroy it, and prevent itself from being extricated. This adds to an already bad problem at the bottom of the well.
It is an object of this invention to provide a fishing tool which can be lowered to snag and retrieve a cable, but which if it catches on the bottom of the well pipe or tubing ("tube" herein) will be triggered so as to retract toward the body of the tool itself where it will no longer constitute an impediment to the withdrawal of the tool from the well.